JPS63303312A - optical attenuation device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a light attenuation means (ii) in a lighting device such as a semiconductor exposure device.

[Prior Art] Conventional light attenuation means include those that change the transmittance by utilizing absorption of a solid such as a glass filter, or those that insert an aperture mechanism in the middle of the optical path and operate the aperture mechanism. There was something that attenuated the intensity of the light.

[Problems to be solved by the invention] However, in the conventional technology as described above, the filter and diaphragm mechanism gradually deteriorate due to irradiation with particularly high energy intensity light, and as a result, the performance of light attenuation becomes unstable. There was a problem with not doing so.

The present invention has been made in view of this point, and it is an object of the present invention to provide an optical attenuation device whose performance is stable over a long period of time.

[Means for Solving the Problems] The present invention includes a chamber means disposed in the middle of the optical path, which is filled with a gas that absorbs light at the wavelength of the incident light beam, and an adjustment means that allows the light beam to pass through the chamber means. The technical point is to attenuate the light intensity by varying the amount of light absorbed at the time.

[Function] In the present invention, since light attenuation is achieved by gas absorption, even if the gas deteriorates due to long-term light irradiation, it is extremely easy to replace the gas. Purified gas can be used at all times, and optical attenuation performance is stable over the long term.

``Embodiments'' Hereinafter, examples of the present invention will be described with reference to the drawings.

First Embodiment FIG. 1 shows the configuration of a first embodiment of the present invention.

In the figure, IO is an attenuation chamber placed in the middle of the optical path of the laser beam LB, and the main body is made of stainless steel. At both ends of the attenuation chamber 10, an entrance window 12 and an exit window 14 made of quartz are provided. They are each installed via an O-ring (not shown). The laser beam LB incident through the entrance window 12 passes through the attenuation chamber 10 and exits from the exit window 14.

A KrF excimer laser with an oscillation line of 249 nm is used as the laser beam LB, and Freon FCII (lichlorofluoromethane) that absorbs the laser beam LB with an oscillation line of 249 nm is sealed inside the attenuation chamber 10. ing.

Further, the damping chamber 10 is equipped with a pressure cage 16 that measures the pressure inside the chamber, and each of the air supply valve 18 and the exhaust valve 20 is adjusted based on the pressure measured by the pressure gauge 16. By doing so, the pressure inside the damping chamber 10 can be controlled.

Next, a gas supply system for injecting the gas into the damping chamber 10 and a gas system for the gas will be described.

First, the gas introduced from A when the pulp 22 is opened passes through the first buffer 24 for pressure adjustment, and then the filter 2
6 and the second buffer 28 respectively, and the air supply valve 18
After the gas flow rate is further controlled by a mass flow controller (MFC) 30, the gas is injected into the attenuation chamber 1o. Filter 26 is configured to remove degraded components of the gas passing through it.

On the other hand, the gas exhausted from the exhaust valve 20 is reduced in pressure by an accumulator 32, passes through a circulation pump 34, and is reintroduced into the buffer 24 through a valve 38. When replacing the circulating waste, it is discharged from the valve 36 to B.

Note that the circulation pump 34 is for circulating the gas exhausted from the exhaust valve 2o and sending it out again to the air supply valve 38. The opening and closing operations of the valve 36 and the valve 38 are used to discharge and circulate the gas. Adjustments can be made.

Each of the above-mentioned components is connected by a gas pipe 40.

Next, the operation of the first embodiment will be explained based on a test operation with reference to FIG. 2.

FIG. 2 shows a time chart showing the relationship between the opening and closing operations of the air supply valve 18 and the exhaust valve 20, the gas pressure in the damping chamber 1θ, and the transmittance of the laser beam LB passing through the damping chamber 1θ. has been done.

A predetermined amount of gas is sealed in advance in the damping chamber 10, and the air supply valve 18 and exhaust valve 20 are closed until time T.
Suppose that it is closed and the internal pressure remains constant.

After this, when the exhaust valve 20 is opened from time TI to 12, the pressure inside the attenuation chamber 10 decreases, and on the contrary, the laser beam L passing through the attenuation chamber 10 decreases.
The transmittance of B increases.

Next, when both the air supply and exhaust valves 18.20 are closed from time T2 to time T3, the pressure during this period remains constant and the transmittance of the laser beam LB does not change.

After that, when the air supply valve 18 is opened from time T3 to T4 and a constant flow rate of waste is supplied into the damping chamber 10, the pressure inside the damping chamber 10 rises at a constant rate. Conversely, the transmittance of the laser beam LB passing through the attenuation chamber 10 decreases.

Next, when the air supply valve 18 is closed after time T4, both the internal pressure of the attenuation chamber 10 and the transmittance of the laser beam LB do not change and maintain constant values as in the initial state.

The basic operation in this embodiment is based on the effect described above. That is, by utilizing the fact that the transmittance of the laser beam LB changes depending on the internal pressure of the attenuation chamber 10, the internal pressure of the attenuation chamber 10 is adjusted by opening and closing the air supply valve 18 and the exhaust valve 20, and the final The laser beam L passing through the attenuation chamber 10 at
This is to control the degree of attenuation of B.

Next, the overall operation of the first embodiment will be explained.

First, the exhaust valve 20 and the valve 36 are closed, and the k% valve 18. Valve 22. With valve 38 open,
Gas is introduced from A, first buffer 24, filter 26
．． Gas is injected into the damping chamber 10 via the second buffer 28 and mass flow controller 30.

Next, while measuring the internal pressure of the damping chamber 10 with the pressure gauge 16-, the degree of opening and closing of the air supply valve 18 and the exhaust valve 20 is adjusted to bring the internal pressure of the damping chamber 10 to a predetermined pressure. The laser beam LB is made incident on the attenuation chamber 10 and is allowed to pass therethrough. Such an operation causes the intensity of the laser beam LB to be attenuated.

Note that the predetermined pressure is determined by calculating the amount of attenuation of the laser beam LB passing through the attenuation chamber 10 from the optical absorption rate of the gas sealed in the attenuation chamber 10 and the optical path length of the laser beam LB inside the attenuation chamber 10, and based on the amount of attenuation. It is estimated that

Thereafter, based on the measured value of the pressure gauge 16, the opening/closing degrees of the air supply valve 18 and the exhaust valve 20 are adjusted so that the pressure of the waste in the damping chamber 10 reaches a desired value, and the pressure of the waste in the damping chamber 10 is adjusted. The intensity of the emitted laser beam LB, that is, the amount of light is controlled.

Further, the waste exhausted from the exhaust valve 20 is transferred to the accumulator 32. Gas circulation pump 34. First buffer 24.
Filter 26. The second buffer 28 passes through the mass flow controller 30 to the reheat damping chamber 10. circulate to.

At this time, the filter 26 removes degraded components from the passing gas. When the gas deteriorates, turn on valve 3.
6, the gas inside the damping chamber 10 is evacuated.

In the first embodiment as described above, since the light is attenuated by absorption of the gas sealed in the attenuation chamber 10, even if the gas deteriorates due to passing the laser beam LB, the valve 22 By circulating the gas with the operation of the valve 36 and the action of the filter 26, purified gas can be used at all times, and the optical attenuation performance is stabilized over a long period of time.

In the first embodiment, the gas pressure within the attenuation chamber 10 corresponding to a predetermined amount of light is estimated in advance, and the attenuation chamber 10 is adjusted based on this estimated pressure. The intensity of the output light is controlled by adjusting the pressure within θ, but the sight of the laser beam LB before and after the attenuation chamber 10 is detected by a photoelectric converter, etc., and based on this detection information, the attenuation chamber A similar effect can also be obtained by adjusting the gas pressure within 10.

Furthermore, instead of installing the entrance window 12 and the exit window 14 in a fixed manner, at least one of them is moved in response to the pressure inside the attenuation chamber 10, and the pressure inside the chamber 10 itself is not particularly adjusted. By adjusting the optical path length of the laser beam LB within the attenuation chamber 10, it is fully possible to attenuate the intensity of the output light by varying the amount of light absorbed by the gas.

In addition, the laser beam LB is not limited to an excimer laser with an oscillation FiA of 249 nm, but the same effect can be obtained even if Freon PCI2 (cyclodifluoromethane) or the like is used as an absorption gas and the laser beam with the oscillation line +93 nm is targeted. That's what you get.

Second Embodiment FIG. 3 shows the configuration of a second embodiment of the present invention, 10, 12. +4, 16, 20 and 40 are the same as those in the above-mentioned eleventh embodiment, and the configurations of other similar parts are omitted. Note that the explanation of the same parts as in the first embodiment will be omitted, and only the different parts will be explained in detail.

In the figure, the laser beam LB has an excimer laser r
An oscillation line of 193 nm of F is used, and carbon dioxide (CO2) is used as an absorption gas.
Nitrogen gas (N
2) is used.

Mass flow controllers 30a and 30b respectively control the flow rates of carbon dioxide (CO2) that absorbs the laser beam LB with the oscillation line of 193 nm and nitrogen gas (N2) that does not absorb the same saheem LB. Carbon dioxide (CO2) and nitrogen gas (N2) that have passed through the air supply valves 18a and 18b, respectively, are injected into the damping chamber 10 with their flow rates controlled by the action of these mass flow controllers 30a and 30b. .

Reference numeral 42 denotes a pump, which exhausts the gas in the damping chamber 10 at a constant rate via the exhaust valve 20. At this time, the pressure gauge 16 detects carbon dioxide (CO2) and nitrogen gas (N2) in the damping chamber 10.
), and the air supply valves 18a, 18b and exhaust valve 2 are adjusted so that the pressure is kept constant.
It is designed to adjust 0.

Next, the operation of the second embodiment will be explained.

First, the IJ) air valve 20 is closed, and the air supply valve 18a,
Open I8b to release carbon dioxide (CO2) and nitrogen gas (
N2) through the air supply valve 18a.

181) and into the damping chamber 10 via the mass flow controller 1 to the rollers 30a, 30b, etc., respectively.

After a predetermined amount of gas has been pumped into the damping chamber 10, the exhaust valve 20 is loosened and the pump 42 is pumped at a constant speed.
2: The mixed gas in the damping chamber 10 is inflated with air supply.

Next, based on the pressure of the mixed gas in the damping chamber 10 which is opened in the pressure cage 16, the air supply valve 1
8a, 18b and a pressure valve 20 to keep the pressure in the damping chamber 10 constant.

Then, the mass flow controllers 30a and 30b control the flow rates of the two types of gas to make the partial pressure of carbon dioxide (CO2) for light absorption in the attenuation chamber 10 correspond to the desired output light amount of the laser beam LB. Adjust. The partial pressure of carbon dioxide (CO2) is determined based on the light absorption rate of carbon dioxide and the optical path length of the laser beam LB entering the attenuation chamber 10, as in the first embodiment described above. is calculated and estimated based on the attenuation amount.

After that, the partial pressure of carbon dioxide (CO2) in the damping chamber 10 becomes the desired value, which is estimated based on the measured value from the pressure gauge 16. chamber 10
The intensity of the laser beam LB emitted from the laser beam LB, that is, the amount of light is controlled.

In addition to the effects of the first embodiment described above, the second embodiment has the advantage that the transmittance of the laser beam LB can be controlled over a wide range.

It goes without saying that the same effect can be expected even if carbon dioxide (CO2) and nitrogen gas (N2) are mixed before being introduced into the attenuation chamber 10.

[Effects of the Invention] As described above, according to the present invention, since light is attenuated by gas absorption, there is an effect that performance is stabilized over a long period of time.

[Brief Description of the Drawings] Fig. 1 is a configuration diagram showing a first embodiment of the present invention, Fig. 'iS2 is an explanatory diagram showing the operation of the embodiment, and Fig. 3 is a configuration diagram showing a second embodiment of the present invention. It is a diagram. "Explanation of symbols of main parts" 10... Attenuation chamber, 12... Entrance window, 14...
・Ejection window, 16... Pressure gauge, 18... Air supply valve, 20... Exhaust valve, LB... Laserheem agent Patent attorney Tadashi Sato Toshibetsu 2nd view 3rd figure

Claims (3)

[Claims] (1) A light attenuation device that attenuates the intensity of an incident light beam and emits the light, the chamber means being filled with a gas that absorbs light having the wavelength of the incident light beam and disposed in the middle of the optical path; and adjusting means for varying the amount of light absorbed when the light passes through the chamber means. (2) Claim 1, wherein the adjusting means adjusts the pressure or partial pressure of the gas within the chamber means, or the optical path length of the light beam within the chamber means. The optical attenuation device described. (3) The gas is not flammable, corrosive, or toxic, or is made of a component that is extremely weak and undergoes almost no chemical change upon absorption of light. The optical attenuation device according to item 1 or 2.